Hip joint device and method

ABSTRACT

A medical device for implantation in a hip joint of a patient. The medical device comprises an inner and an outer surface, wherein a contacting portion of said inner surface is spherical and adapted to face a center of the hip joint when said medical device is implanted. The medical device is adapted to receive a caput femur or a prosthetic caput femur having a spherical portion. Said medical device comprises at least one extending portion adapted to clasp the caput femur, or prosthetic caput femur, for restraining said caput femur, or said prosthetic caput femur in said medical device. The extending portion comprises an elastic portion, and the medical device is adapted to release the caput femur or prosthetic caput femur from said medical device by deflecting said at least extending portion when a predetermined strain is placed on said medical device by abnormal movement of the hip joint caused by the patient.

This application is a continuation of U.S. application Ser. No.14/857,860, filed Sep. 18, 2015, which is a continuation of U.S.application Ser. No. 13/383,300 filed on Jan. 10, 2012, and issued onSep. 22, 2015, as U.S. Pat. No. 9,138,320, which is the U.S. nationalphase of International Application No. PCT/SE10/50831, filed Jul. 12,2010, Which designated the U.S. and claims the benefit of U.S.Provisional Application Nos. 61/229,739, 61/229,743, 61/229,745,61/229,746, 61/229,747, 61/229,748, 61/229,751, 61/229,752, 61/229,755,61/229,761, 61/229,767, 61/229,778, 61/229,786, 61/229,789, 61/229,796,61/229,735, 61/229,738, all filed Jul. 30, 2009 and priority hornSwedish Patent Application Nos. 0900958-0, 0900978-8, 0900976-2,0900974-7, 0900973-9, 0900972-1, 0900970-5, 0900969-7, 0900968-9,0900966-3, 0900965-5, 0900963-0, 0900962-2, 0900960-6, 0900959-8,0900957-2, 0900981-2, all filed Jul. 10, 2009, the entire contents ofthe above applications are hereby incorporated by reference in thisapplication.

TECHNICAL FIELD

The present invention relates generally to medical devices forimplantation in a hip joint.

BACKGROUND ART

The hip joint is a synovial joint joining the pelvis to the proximalportion of the femoral bone. Synovial joints are the most common typesof joints in mammals, and are typical of nearly all limb joints. Thecontacting surfaces of said the pelvic, the acetabulum, and thecontacting surface of the femoral bone, the caput femur, are smooth androunded, and covered by articular cartilage. A synovial membrane,encapsulates the joint, forming a hip joint cavity, which containssynovial fluid. Outside the synovial membrane is a fibrous capsule andligaments, forming an articular capsule.

There are both natural and pathological processes leading todeteriorated joint function. With age and wear, the articular cartilagebecomes less effective as a shock absorber and a lubricated surface.Different degenerative joint diseases, such as arthritis,osteoarthritis, or osteoarthrosis, accelerate deterioration.

Hip joint Osteoarthritis is a syndrome in which low-grade inflammationresults in pain in the hip joints, caused by abnormal wearing of theCartilage that acts as a cushion inside if the hip joint. This abnormalwearing of the cartilage also results in a decrease of the jointslubricating fluid called Synovial fluid. Hip joint Osteoarthritis isestimated to affect 80% of all people over 65 years of age, in more orless serious forms.

The present treatment for hip osteoarthritis comprises NSAID drugs,local injections of Hyaluronic acid or Glucocorticoid to helplubricating the hip joint and replacing parts of the hip joint with aprosthesis through hip joint surgery.

The replacing of parts of the hip joint is one of the most commonsurgeries to date performed at hundreds of thousands of patients in theworld every year. The most common method comprises placing a metalprosthesis in Femur and a plastic bowl in Acetabulum. This operation isdone through an incision in the hip and upper thigh and through FasciaIata and the lateral muscles of the thigh. To get access to the joint,the supporting Capsule attached to Femur and Ilium needs to bepenetrated, making it difficult to get a fully functional joint afterthe surgery. Femur is then cut at the neck with a bone saw and theprosthesis is placed in femur either with bone cement or without.Acetabulum is slightly enlarged using an Acetabular reamer, and theplastic bowl is positioned using screws or bone cement.

The complications after hip joint surgery includes dislocation of thehip joint and loosening of the prosthesis from its fixation in thefermoral bone. The loosening and/or dislocation of the prosthesis couldbe induced by an abnormal strain being placed on the hip joint from e.g.the patient falling or making a rapid movement of the hip, or by abodily macrophage reaction.

SUMMARY

A medical device for implantation in a hip joint of a patient isprovided. The medical device is adapted to be fixated to the pelvic boneof the patient. The medical device comprises an inner and an outersurface, a contacting portion of the inner surface is spherical andadapted to face the center of the hip joint when said medical device isimplanted, and said medical device is adapted to receive a caput femuror a prosthetic caput femur having a spherical portion. The medicaldevice comprises at least one extending portion adapted to clasp thecaput femur, or prosthetic caput femur, for restraining said caputfemur, or prosthetic caput femur in said medical device. The medicaldevice is adapted to release the caput femur or prosthetic caput femurfrom the medical device when a predetermined strain is placed on themedical device. The ability of the medical device to release the caputfemur or prosthetic caput femur from the medical device when apredetermined strain is placed on the medical device reduces the riskthat the prosthesis is loosened by an abnormal strain being placed onthe hip joint, from e.g. the patient falling or making a rapid movementof the hip.

According to another embodiment, the medical device is adapted toreceive a caput femur or an artificial replacement therefor, having acollum femur or artificial collum femur fixated to said sphericalportion of said caput femur or artificial replacement therefor. Theinner surface comprises an equator line, being the largest circularcircumference of said inner surface. The at least one extending portionpasses beyond said equator line, such that the end portion of saidcontacting portion of said inner surface forms a circular extension linehaving a smaller circumference than said equator line. The at least oneextending portion longitudinal extends discontinuously along saidequator line, such that a portion of said collum femur or prostheticcollum femur can be placed between said extension line and said equatorline.

The extension line can be placed distal to the equator line, when themedical device is implanted.

The extending portion adapted to clasp the caput femur could comprise anelastic portion, which for example could comprise an elastic material, aspring or an elastic band.

The elastic band cold be adapted to at least partly encircle the caputfemur.

According to another embodiment, the extending portion could comprise amovable portion adapted to clasp the caput femur, and further adapted tomove such that said movable portion releases the caput femur orprosthetic caput femur from said medical device, when a predeterminedstrain is placed on said medical device.

According to yet another embodiment the movable portion could comprise amovable part.

According to yet another embodiment the extending portion could compriseat least one magnet adapted to hold the caput femur in the medicaldevice.

According to yet another embodiment the extending portion could comprisea rupture device adapted to fail at a pre-determined strain. The rupturedevice could for example comprise a rupture band, or a rupture pin.

According to yet another embodiment, the extending portion could beadapted to slide against the caput femur, or adapted to roll against thecaput femur. The extending portion adapted to roll against the caputfemur could comprise a ball shaped part.

According to one embodiment, the at least one extending portion extendslongitudinally along said equator line, dorsal to a lateral-medial axisof pelvis.

According to one embodiment, the at least one extending portion extendslongitudinally along said equator line, dorsal to the lateral-medialaxis and proximal to the lateral-medial axis of pelvis.

According to one embodiment, the at least one extending portion extendslongitudinally along said equator line, dorsal to the lateral-medialaxis and distal to the lateral-medial axis of pelvis.

According to one embodiment, the at least one extending portion extendslongitudinally along said equator line, dorsal to the lateral-medialaxis and distal to the lateral-medial axis of the pelvis, and oneextending portion extends dorsal to the lateral-medial axis and proximalto the lateral-medial axis of the pelvis.

According to one embodiment, the at least one extending portion extendslongitudinally along said equator line, in the proximal quadrantthereof.

According to one embodiment, the at least one extending portion extendslongitudinally along said equator line, in the distal quadrant thereof.

According to one embodiment, the two extending portions extendslongitudinally along said equator line, in the distal and proximalquadrant thereof.

The at least one extending portion could extend longitudinally along theequator line, in the proximal and dorsal quadrant thereof.

The at least one extending portion could extend longitudinally alongsaid equator line, in the distal and dorsal quadrant thereof.

The at least one extending portion could extend longitudinally along theequator line, in the distal, dorsal and proximal quadrant thereof.

According to one embodiment at least a first portion of the medicaldevice is an extending portion, extending beyond the circular equatorline, and at least a second portion is a portion not extending beyondthe circular equator line, wherein said second portion longitudinallyextends along at least ¼ of said circular equator line.

In any of the embodiments herein, the at least first portion of themedical device could be an extending portion, extending beyond saidcircular equator line, and at least a second portion could be a portionnot extending beyond said circular equator line, wherein said secondportion longitudinally extends along at least ⅓ of said circular equatorline.

In any of the embodiments herein, the at least first portion of themedical device could be an extending portion, extending beyond saidcircular equator line, and at least a second portion could be a portionnot extending beyond said circular equator line, wherein said secondportion longitudinally extends along at least ½ of said circular equatorline.

In any of the embodiments herein, the at least first portion of themedical device could be an extending portion, extending beyond saidcircular equator line, and at least a second portion could be a portionnot extending beyond said circular equator line, wherein said secondportion longitudinally extends along at least ¼ of said, circularequator line.

In any of the embodiments herein, the at least first portion of themedical device could be an extending portion, extending beyond saidcircular equator line, and at least a second portion could be a portionnot extending beyond said circular equator line, wherein said firstportion longitudinally extends along at least ⅓ of said circular equatorline.

In any of the embodiments herein, the at least first portion of themedical device could be an extending portion, extending beyond saidcircular equator line, and at least a second portion could be a portionnot extending beyond said circular equator line, wherein said firstportion longitudinally extends along at least ½ of said circular equatorline.

In any of the embodiments herein, the at least first portion of themedical device could be an extending portion, extending beyond saidcircular equator line, and at least a second portion could be a portionnot extending beyond said circular equator line, wherein said firstportion longitudinally extends along at least 1/10 of said circularequator line.

In any of the embodiments herein, the at least one first portion of saidmedical device could be an extending portion, extending beyond saidcircular equator line, and at least a second portion could be a portionnot extending beyond said circular equator line. The first portion couldlongitudinally extend along at least 1/10 of said circular equator line,and said second portion could longitudinally extend along at least ¼ ofsaid circular equator line.

In any of the embodiments herein, the at least two first portions ofsaid medical device could be extending portions, extending beyond saidcircular equator line, and at least a second portion could be a portionnot extending beyond said circular equator line. The first portions eachlongitudinally extending along at least 1/10 of said circular equatorline, and said second portion longitudinally extends along at least ¼ ofsaid circular equator line.

According to one embodiment at least two first portions of the medicaldevice could be extending portions, extending beyond the circularequator line, and wherein one of the extending portions extends furtherthan the other extending portion.

The medical device could according to one embodiment further comprisetwo second portions not extending beyond said circular equator line. Thetwo first extending portions could longitudinally extend along theequator line between the two second portions.

According to one embodiment, the medical device further comprises atleast one hole adapted to receive a fixating member, for fixating saidmedical device to the pelvic bone. The hole could be adapted to receivea screw for fixating said medical device to the pelvis.

In yet another embodiment, the medical device could comprise at leastone extending portion adapted to clasp the caput femur, or a prostheticcaput femur, for restraining said caput femur, or prosthetic caput femurin said medical device. The medical device could be adapted to releasethe caput femur or prosthetic caput femur from the medical device when apredetermined strain is placed on said medical device.

The extending portion could comprise an elastic portion, which forexample could comprise an elastic material, a spring or an elastic bandwhich could be adapted to at least partly encircle said ball shapedpiece.

According to another embodiment, the extending portion could comprise amovable portion which could comprise a movable part.

According to another embodiment, the extending portion could comprise amagnet adapted to hold said first piece to said second piece.

According to yet another embodiment, the extending portion couldcomprise a rupture device adapted to fail at a pre-determined strain.The rupture device could for example comprise a rupture band or arupture pin.

According to one embodiment, the medical device could comprises multipleholding members. Said multiple holding members could comprise at leastone holding member adapted to slide against the caput femur, orprosthetic caput femur or at least one holding member adapted to rollagainst the caput femur, or prosthetic caput femur. The holding memberadapted to roll could comprise a ball shaped holding member.

The medical device could according to any one of the precedingembodiments have at least one of extending portion, when implanted, isadapted to be placed such as to restrict the motion range of the hipjoint, and wherein said at least one extending portion is adapted to beplaced or shaped such that at least one of adduction, abduction,flexion, extension, a combination of flexion and adduction or abduction,a combination of extension and adduction or abduction, rotation in,rotation out, and any combination of rotation in or out and the otherdescribed movements, is restricted more degrees from maximal movementthan any of the other.

According to one embodiment, the medical device comprises a prostheticcaput femur being ball shaped and adapted to be at least partly placedinside said inner surface, being bowl shaped, wherein: said innersurface comprises an equator line, being the largest circularcircumference of said inner surface, said at least one extending portionof said inner surface passes beyond said equator line, such that the endportion of a contacting portion of said inner surface, the most distalportion of said inner surface adapted to contact the prosthetic caputfemur, when the inner surface is placed symmetrically onto theprosthetic caput femur, forms a circular extension line parallel to saidequator line having a smaller circumference than said equator line, andsaid at least one extending portion is constructed according to at leastone of the following alternatives; a) circumferentially extendsdiscontinuously along said equator line having enough circumferentialdistance lacking any extending portion and b) extends with differentdistal extension in different extending portions or part of such portionof said circumferential extension.

According to one embodiment medical device comprises an inner surfacecomprising an equator line, being the largest circular circumference ofsaid inner surface. The at least one extending portion of said innersurface passes beyond said equator line, such that the end portion of acontacting portion of said inner surface, the most distal portion ofsaid inner surface adapted to contact a prosthetic caput femur, when theinner surface is placed symmetrically onto the prosthetic caput femur,forms a circular extension line parallel to said equator line having asmaller circumference than said equator line, and said at least oneextending portion extends with different distal extension over thecircumferential extension, thus adapted to restrict movements clearlydifferent in different directions of movement, due to different distalextension of different extending portions in said circumferentialextension.

According to another embodiment, the medical device comprises an innersurface comprising an equator line, being the largest circularcircumference of said inner surface, at least one extending portion ofsaid inner surface passes beyond said equator line, such that the endportion of a contacting portion of said inner surface, the most distalportion of said inner surface adapted to contact a prosthetic caputfemur, when the inner surface is placed symmetrically onto theprosthetic caput femur, forms a circular extension line parallel to saidequator line having a smaller circumference than said equator line, andpart of said at least one extending portion extends with differentdistal extension over the circumferential extension, thus adapted torestrict movements clearly different in different directions ofmovement, due to different distal extension of different parts of suchextending portion in said circumferential extension.

According to one embodiment the medical device for implantation in a hipjoint comprises a locking member for locking an artificial replacement,of an acetabulum in a hip joint to clasp a caput femur or an artificialreplacement therefore, when implanted in a hip joint of a patient,wherein said locking member is adapted to in situ assist in the fixationof the medical device, wherein: said inner surface comprises an equatorline, being the largest circular circumference of said inner surface, atleast one extending portion of said inner surface passes beyond saidequator line, such that the end portion of a contacting portion of saidinner surface, the most distal portion of said inner surface adapted tocontact a caput femur or prosthetic caput femur, when the inner surfaceis placed symmetrically onto the prosthetic caput femur, forms acircular extension line parallel to said equator line having a smallercircumference than said equator line, said locking member is adapted tolock said caput femur or prosthetic caput femur such that the caputfemur or prosthetic caput femur remains clasped and restrained in saidinner surface, and said locking member is adapted to lock said at leastone extension portion, when implanted, having at least the end portionof the extension portion radially fixed within said circular extensionline.

According to one embodiment the locking member is adapted to lock in atleast a first and second locking position.

According to one embodiment the locking member is adapted to lock in atleast a first and a second locking position, and wherein said lockingmember is adapted to; in said first locking position, lock an artificialcaput femur surface having at least one extending portion, to a firstsize caput and/or collum femur, and in said second locking position,lock said artificial caput femur surface, to a second smaller size caputfemur and/or collum femur.

The hip joint having a collum femur, having a first axial distributionleading to a caput femur, wherein said collum femur is placed distal tothe caput femur, a center axis of the collum and caput femur in linewith the first axial distribution being the caput femur center axis,wherein the caput femur has a substantially ball shaped configurationwith an outer maximum radius perpendicular to the caput femur centeraxis, the caput femur being placed in a bowl shaped acetabulum, havingan opening, wherein the bowl shaped acetabulum has a second axialdistribution with an acetabulum center axis from the center of thebottom of the acetabulum bowl and following the center of the bowltowards the center of the opening of the bowl, towards the caput femur,wherein the acetabulum bowl has an inner maximum radius perpendicular tothe acetabulum center axis, wherein the caput femur center axis is inline/aligned with the acetabulum center axis, in a special centeredposition, when the caput femur is placed; aligned, centered andsymmetrical in the acetabulum bowl in the hip joint, the aligned centeraxis is defined as the hip joint center axis, wherein the caput femurand the acetabulum has one hip joint surface each, placed towards andcontacting each other, wherein the hip joint surfaces carrying weight inthe hip joint are the weight carrying surfaces, wherein the outermaximum radius of the caput femur is forming a circular extending,maximum caput femur radius circle, extending perpendicular to the hipjoint center axis, defining a maximum caput femur radius cross-sectionperpendicular to the hip joint center axis, wherein: said medical devicecomprises at least one artificial hip joint surface, adapted to at leastpartly replace at least one of the hip joint surfaces, said artificialhip joint surface at least partly being hollow and having an inner andouter surface, wherein said artificial hip joint surface has anartificial hip joint surface center axis aligned with the hip jointcenter axis when the hip joint is placed in the special centeredposition, when at least one of said artificial hip joint surfaces isimplanted in the hip joint, with the caput femur or an artificial caputfemur surface placed; aligned, centered and symmetrical in theacetabulum bowl or an artificial acetabulum surface in the hip joint,wherein said medical device comprises a central part and a surroundingpart, the central part being aligned with the artificial hip jointsurface center axis and the surrounding part surrounding the surface ofthe caput femur or an artificial caput femur surface not including thecentral part, wherein the caput femur or an artificial caput femursurface, has a maximum caput femur radius cross-section, in which theouter maximum radius of the caput femur or said artificial caput femursurface is forming a circular extending maximum caput femur orartificial caput femur radius circle, extending perpendicular to the hipjoint center axis, defining the maximum caput femur radius cross-sectionperpendicular to the hip joint center axis or perpendicular to saidartificial hip joint surface center axis, when the hip joint is placedin said special centered position, wherein the surrounding part of saidat least one artificial hip joint surface comprises at least one firstextending portion of the artificial hip joint surface for extending indistal direction at least partly beyond the maximum caput femur radiuscross-section, when the hip joint is placed in said special centeredposition, when at least one of the artificial hip joint surfaces isimplanted in the hip joint, wherein said at least one first beyond partis adapted to have a closest perpendicular distance to said artificialhip joint surface center axis, being smaller than an inner maximumdistance, extending perpendicularly from said artificial hip jointsurface center axis to said inner surface of said artificial hip jointsurface, when the hip joint is placed in the above mentioned specialcentered position and said artificial hip joint surface is placed in afunctional position in the hip joint thus adapted to create and creatinga more stable position of said artificial hip joint surface when mountedin the hip joint.

According to one embodiment, the hip joint has a caput femur hip jointsurface party being the contacting surface of the hip joint, the hipjoint further having a collum femur, having a first axial distributionleading to a caput femur, wherein a center axis of the first axialdistribution of the the collum femur and the caput femur, being thecaput femur center axis, wherein the collum femur is placed more distalthan caput femur, wherein; said medical device comprises an artificialcaput lemur surface being hollow, having a major opening adapted to bedirected towards the caput femur or a surgically modified caput femur,wherein said artificial caput femur surface is adapted to replace acaput femur hip joint surface, wherein said artificial caput femursurface further having; a medical device caput center axis passingthrough said major opening being aligned with the caput femur centeraxis, when said medical device is implanted in a functional position inthe hip joint, wherein said medical device comprises a central part anda surrounding part, the central part being aligned with the medicaldevice center axis and the surrounding part surrounding the surface ofthe caput femur or the surgically modified caput femur not including thecentral part and wherein said medical device further comprising an innersurface adapted to have a first distal distance extendingperpendicularly from said medical device caput center axis to said innersurface of the surrounding part of said artificial caput femur surface,said first distal distance being shorter than a second proximal distanceextending perpendicularly from said medical device caput center axis tosaid inner surface of said artificial caput femur surface, said secondproximal distance extending from a more proximal position on saidmedical device caput center axis than said first distal distance, beingthe second proximal distance, when said artificial caput femur surfaceis implanted in said functional position in the hip joint.

The hip joint has an acetabulum, being a bowl shaped contacting surfaceof the hip joint comprising a substantially circular major opening indistal direction of the acetabulum in the hip joint and a bottom centerpoint in said bowl shaped acetabulum proximally in the hip joint,wherein an acetabulum center axis extends from the bottom point throughthe center point of the substantially circular opening, wherein theacetabulum has a weight carrying surface contacting a ball shaped caputfemur located in the acetabulum bowl in the hip joint wherein the caputfemur is connected to the collum femur, and the collum femur has acenter axis aligned with a caput femur center axis, wherein; saidmedical device comprises an artificial acetabulum surface adapted toreplace the weight carrying surface of the acetabulum, wherein saidartificial acetabulum surface is hollow and has a major acetabulumopening adapted to be directed towards the caput femur or an artificialreplacement of at least the surface of the caput femur, wherein saidartificial acetabulum surface is adapted to receive a caput femur or anartificial replacement of at least the surface of the caput femur, insaid hollow artificial acetabulum surface, when implanted in the hipjoint, said artificial acetabulum surface having; a medical deviceacetabulum center axis, adapted to be aligned with the acetabulum centeraxis, when said artificial acetabulum surface is placed in the hipjoint, and an inner surface adapted to have a first distal distanceextending perpendicularly from said medical device acetabulum centeraxis, to said inner surface of said artificial acetabulum surface, saidfirst distal distance being shorter than a second proximal distanceextending perpendicularly from said medical device acetabulum centeraxis to said inner surface of said artificial acetabulum surface, saidsecond proximal distance extending from more proximal position on saidmedical device acetabulum center axis than said first distal distance,when said artificial acetabulum surface is implanted functionally in thehip joint, wherein said artificial acetabulum surface is adapted toreceive in the hollow artificial acetabulum surface the caput femur oran artificial replacement of at least the surface of the caput femur,when implanted in the hip joint, for achieving a functional hip joint.

According to one embodiment the least one of extending portion isadapted to have at least one of its shape or position such that therestriction of movement range of the hip joint, in degrees from maximalmovement, is restricted more in at least one predefined direction thanin any other direction, when implanted.

A method using a medical device according to any of the preceding claimsis further provided. The method comprise cutting the skin in the hipregion dissecting the hip joint implanting the medical device in a hipjoint of a patient, fixating the device to the pelvic bone of thepatient, and wherein said medical device comprises an inner and an outersurface, having a contacting portion of said inner surface beingspherical and bowl shaped facing the inner surface to the center of thehip joint having at least one extending portion, extending a contactingportion for contacting the caput femur or a prosthetic replacementtherefore, placing a caput femur or a prosthetic replacement thereforehaving a spherical portion, such that said extending contacting portionof said inner surface is clasping said spherical portion of said caputfemur, or a prosthetic replacement therefore, such that said caputfemur, or a prosthetic replacement therefore is restrained in said bowlshaped inner surface.

According to one embodiment the method comprises, placing for contactingtowards said inner surface said caput femur or artificial replacementtherefore, said inner surface comprising an equator line being thelargest circular circumference of said inner contacting surface, placingand passing with said at least one extending portion beyond said equatorline, such that the end portion of said contacting portion of said innersurface forms a circular extension line having a parallel smallercircumference than said equator line, the end portion being the mostdistal portion of the inner surface being in contact with said caputfemur or artificial replacement therefore, when said said caput femur orartificial replacement therefore is placed symmetrically in said innersurface, and wherein said at feast one extending portion is extendingcircumferentially discontinuously along said equator line, such that themethod involves, placing a portion of said collum femur or prostheticreplacement therefore between said extension line and said equator linewhen moving said caput femur or artificial replacement therefore inrelation to said inner surface.

According to one embodiment, the said at least one extending portion ismounted according to at least one of the following alternatives: a)extending circumferentially discontinuously along said equator linehaving enough circumferential distance lacking any extending portion andb) extending with different distal extension in different extendingportions or part of such portion of said circumferential extension.

According to one embodiment the method comprises using a medical devicefor implantation in a hip joint according to any of the precedingclaims, comprising a locking member for locking an artificialreplacement of an acetabulum in a hip joint to clasp a caput femur or anartificial replacement therefore, when implanted in a hip joint of apatient; wherein said locking member is adapted to in situ assist in thefixation of the medical device, said artificial acetabulum comprising aninner surface comprising an equator line, being the largest circularcircumference of said inner surface, wherein at least one extendingportion of said inner surface passes beyond said equator line, such thatthe end portion of a contacting portion of said inner surface, the mostdistal portion of said inner surface adapted to contact a caput femur orartificial caput femur forms a circular extension line parallel to saidequator line having a smaller circumference than said equator line, whenthe inner surface is placed symmetrically onto the prosthetic caputfemur, wherein the method comprising the following steps: cutting theskin in the hip region dissecting the hip jointimplanting the medicaldevice in a hip joint of a patient fixating the artificial replacementof an acetabulum to the pelvic bone of the patient comprising an innerand an outer surface, having a contacting portion of said inner surfacebeing spherical and bowl shaped, facing the inner surface to the centerof the hip joint having at least one extending portion, extending acontacting portion for contacting the caput femur or a prostheticreplacement therefore, placing a caput femur or an artificialreplacement therefore having a spherical portion, such that saidextending contacting portion of said inner surface is clasping saidspherical portion of said caput femur, or an artificial replacementtherefore, placing said locking member such that said caput femur, orartificial replacement therefore is restrained in said bowl shaped innersurface, and locking said caput femur or artificial caput femur in saidclasped and restrained position in said inner surface, by fixatingradially at least the end portion of the at least one extension portionwithin said circular extension line.

According to one embodiment the method comprises clasping said caputfemur, or artificial replacement therefore in said medical device innersurface, and releasing said caput femur or artificial replacementtherefore when a predetermined strain is placed onto said clasped caputfemur or artificial replacement therefore.

Please note that any embodiment or part of embodiment, feature, method,associated system, part of system described herein or in the associatedfigures may be combined in any way.

BRIEF DESCRIPTION OF DRAWINGS

The invention is now described, by way of example, with reference to theaccompanying drawings, in which:

FIG. 1 shows pelvis in a frontal view,

FIG. 2a shows pelvis in a lateral view,

FIG. 2b shows pelvis in a perspective view from below,

FIG. 2c shows the acetabulum, schematically,

FIG. 2d shows tire acetabulum, schematically,

FIG. 3 shows the pelvis in a lateral view,

FIG. 4 shows the medical device according to one embodiment, in aperspective view,

FIG. 5 shows the medical device according to one embodiment, whenfixated to the pelvic bone.

FIG. 6a shows pelvis in a frontal view, when medical device according totwo embodiments have been implanted,

FIG. 6b shows pelvis in a frontal view, when medical device according totwo further embodiments have been implanted,

FIG. 7 shows pelvis in a frontal view, when medical device according totwo embodiments have been implanted,

FIG. 8 shows a medical device according to one embodiment when placed ona prosthetic caput femur fixated in the femoral bone.

FIG. 9a shows pelvis in a lateral view, when the medical device isimplanted,

FIG. 9b shows pelvis in a lateral view, when the medical device isimplanted,

FIG. 10 shows pelvis in a lateral view, when the medical device isimplanted,

FIG. 11 shows pelvis in a lateral view, when the medical device isimplanted,

FIG. 12 shows pelvis in a lateral view, when the medical device isimplanted,

FIG. 13 shows the medical device according to yet another embodiment,

FIG. 14a shows the medical device according to one embodiment with twoextending portions,

FIG. 14b shows the medical device according to one embodiment with threeextending portions,

FIG. 14c shows the medical device according to one embodiment with threeextending portions,

FIG. 14d shows the medical device according to one embodiment with fourextending portions,

FIG. 14e shows the medical device according to one embodiment with twoextending portions,

FIG. 14f shows the medical device according to one embodiment with threeextending portions,

FIG. 15a shows the hip joint in section when a medical device isimplanted, in its first state,

FIG. 15b shows the hip joint in section when a medical device isimplanted, in its second state,

FIG. 16 shows the hip joint in section when a medical device isimplanted, in its first state,

FIG. 17 shows the hip joint in section when a medical device isimplanted, in its second state,

FIG. 18 shows the medical device in section, when in its first state,

FIG. 19 shows the hip joint in section when a medical device isimplanted, in its first state,

FIG. 20 shows the hip joint in section when a medical device isimplanted, in its second state,

FIG. 21 shows the hip joint in section when a medical device isimplanted, in its first state,

FIG. 22 shows the hip joint in section when a medical device isimplanted, in its second state,

FIG. 23a shows the hip joint in section when a medical device isimplanted, in its first state,

FIG. 23b shows a medical device in section when in the first state,

FIG. 24a shows the hip joint in section when a medical device isimplanted, in its second state,

FIG. 24b shows a medical device in section when in its second state,

FIG. 25 shows the hip joint in section when a medical device isimplanted, in its first state,

FIG. 26 shows the hip joint in section when a medical device isimplanted, in its second state,

FIG. 27 shows the hip joint in section when a medical device isimplanted, in its first state,

FIG. 28 shows the hip joint in section when a medical device isimplanted, in its second state,

FIG. 29 shows the hip joint in section when a medical device isimplanted, in its first state,

FIG. 30 shows the hip joint in section when a medical device isimplanted, in its second state,

FIG. 31 shows the hip joint in section when a medical device isimplanted, in its first state,

FIG. 32 shows the hip joint in section when a medical device isimplanted, in its second state,

FIG. 33 shows the hip joint in section when a medical device isimplanted, in its first state,

FIG. 34 shows the hip joint in section when a medical device isimplanted, in its first state,

FIG. 35 shows the hip joint in section when a medical device isimplanted, in its second state.

DETAILED DESCRIPTION

The hip joint is a synovial ball and socket joint which permits a largemotion range for allowing a plurality of different movements of thelower limb. From a neutral position the following movements of the hipjoint are normally possible: Lateral or external rotation, 30° with thehip extended, 50° with the hip flexed, medial or internal rotation 40°,extension or retroversion 20°, flexion or anteversion 140°, abduction50° with hip extended, 80° with hip flexed, adduction 30° with hipextended, 20° with hip flexed.

When replacing the natural hip joint with a prosthetic hip joint thedepth of the prosthetic acetabulum will affect the motion range, thedeeper the acetabulum bowl is made the more restrictive it is to themotion range. A deeper bowl has the advantage of reducing the risk ofhip joint luxation, the risk of which is a major drawback withprosthetic hips of today.

The anatomy of the hip joint and its surroundings is further disclosedin: Marieb et al., Human Anatomy, 2003, Benjamin Cummings, SanFrancisco, pages 195-202 and in Moore et al., Clinically orientedanatomy, 1999, Iippincott, Williams & Wilkins, Baltimore, pages 501-653,both hereby incorporated by reference.

Functional hip movements are to be understood as movements of the hipthat at least partly correspond to the natural movements of the hip. Onsome occasions the natural movements of the hip joint might be somewhatlimited or altered after hip joint surgery, which makes the functionalhip movements of a hip joint with prosthetic surfaces somewhat differentthan the functional hip movements of a natural hip joint.

Everyday activities is to be understood as activities which are notconnected to any extreme movements, such that some physical sportsrequire. For example, everyday activities comprise: walking, sitting,cycling etc.

The functional position of an implantable medical device or prosthesisis the position in which the hip joint can perform functional hipmovements. The final position is to be understood as a functionalposition in which the medical device needs no further position change tofunction.

Elastic deformation is when a material deforms under stress (e.g.external forces), but returns to its original shape when the stress isremoved. A more elastic material is to be understood as a materialhaving a lower modulus of elasticity. The elastic modulus of an objectis defined as the slope of its stress-strain curve in the elasticdeformation region. The elastic modulus is calculated as stress/strain,where stress is the force causing the deformation, divided by the areato which the force is applied; and strain is the ratio of the changecaused by the stress.

Elasticity is to be understood as a materials ability to deform in anelastic way.

Stiffness is to be understood as the resistance of an elastic body todeformation by an applied force.

Biocompatible material is to be understood as being a material with lowlevel of immune response. Biocompatible materials are sometimes alsoreferred to as biomaterials. Analogous is biocompatible metals abiocompatible metal with low immune response such as titanium ortantalum. The biocompatible metal could also be a biocompatible alloycomprising at least one biocompatible metal.

Form fitting is to be understood as an element having a part or sectionwhich is adapted to enable a mechanical connection of said element to atleast one other element using said part or section. Form fittedstructure is a structure of an element which enables form fitting.

In the following a detailed description of embodiments of the presentinvention will be given. In the drawing figures, like reference numeralsdesignate identical or corresponding elements throughout the severalfigures. It will be appreciated that these figures are for illustrationonly and are not in any way restricting the scope of the invention.Thus, any references to direction, such as “up” or “down”, are onlyreferring to the directions shown in the figures. Also, any dimensionsetc. shown in the figures are for illustration purposes.

FIG. 1 shows the pelvis in a frontal view. Pelvis comprises the rightand left hip bone making up the pelvic bone, in turn comprising theSacrum 1803, Ilium 1802, Pubis 1804 and Ischium 1801. The hip jointhouses the right and left acetabulum 8 a,b placed laterally and distallyin the pelvis. The acetabulum 8 a,b being a spherically shaped cavity inthe hip bones making up one of the parts of the hip joint, theacetabulum 8 a,b being adapted to house the caput femur 5, being theproximal portion of the femoral bone 7 having a spherical contactingsurface adapted to be placed in the acetabulum 8 a,b and thus creatingthe operable hip joint. The pelvis has a lateral-medial axis X extendingsubstantially from the bottom of the left acetabulum 8 a to the bottomof the right acetabulum 8 b, the pelvis further having a proximal-distalY axis extending perpendicular to said lateral-medial axis, centrallyand substantially along the length of the patient passing the dorsalportions of the pubic symphysis 1805 and substantially following thespinal cord 1806, intersecting the lateral-medial axis X.

FIG. 2a shows the pelvis in a lateral view, thus displaying theposterior side of Ilium 1802, the anterior side of Ichum 1801, theanterior side of Pubis 1804, and Sacrum 1803 in a strict lateral view.The pelvis has furthermore a frontal-dorsal axis Z being perpendicularto the proximal-distal axis Y and the lateral-medial axis shown in FIG.1, and intersecting them both creating a common origin O for the threeaxis X, Y, Z. The frontal-dorsal axis Z and the proximal-distal axis Ythus being oriented such that a first plane PZ, extending from thefrontal-dorsal axis Z, and a second, plane PY, extending from theproximal-distal axis Y, penetrates through tire acetabulum 8, thusdividing the acetabulum 8 into 4 sections 1807, 1808, 1809 and 1810.

FIG. 2b shows the pelvis in a perspective view from below displaying thelateral-medial axis X passing through the center of the right and leftacetabulum 8. The lateral-medial axis X is perpendicular to thefrontal-dorsal axis Z which also is perpendicular to the proximal-distalaxis Y. A first plane PY extends from the proximal-distal axis Y, thusdividing the acetabulum in half, centrally. A second plane PZ extendsfrom the dorsal-frontal axis Z, thus dividing the acetabulum in half,centrally and perpendicularly to the first plane PY.

FIGS. 2c and 2d shows the acetabulum 8 schematically, and how the planesPY, PZ devides the acetabulum in to quarters with axis X, Y, Z parallelto the X, Y, Z axis disclosed previously. FIG. 2b further disclosesforamen obturatum 1871.

FIG. 3 shows a lateral view of the pelvis and further displaying twoperpendicular axis Y′ and Z′ being two axis with the same origin as theaxis Y and Z, but rotated clockwise at an angle α being 45°. The twoaxis Y′ and Z′ thus dividing the acetabulum 8 into quadrants 1811, 1812,1813 and 1814. The quadrants being a proximal quadrant 1811, a frontalquadrant 1812, a distal quadrant 1813 and a dorsal quadrant 1814.

FIG. 4 shows a medical device for implantation in a hip joint of apatient. The medical device is adapted to be fixated to the pelvic boneof the patient for example by means of an adhesive, such as bone cement,or mechanical fixating members, such as orthopedic screws. The medicaldevice comprises an inner 1827 and an outer 1828 surface. A contactingportion of the inner surface 1827 is spherical and faces the center ofthe hip joint, when the medical device is implanted. The inside of themedical device is adapted to receive a caput femur or a prostheticreplacement therefor having a spherical portion, and the sphericalcontacting portion of the inner surface 1827 is adapted to be in contactwith a spherical portion of the outer surface of the caput femur or aprosthetic replacement therefor. The medical device, according to theembodiment shown in FIG. 4 comprises two extending portions 1823 a,b,extending the contacting portion of the inner surface 1827′ such thatthe extending portions 1823 a,b clasps the spherical portion of caputfemur or a prosthetic replacement therefor, for restraining thespherical portion in the medical device. The medical device is adaptedto receive the caput femur or a prosthetic replacement therefor, havinga collum femur or prosthetic collum femur fixated to the sphericalportion of the caput femur or prosthetic replacement therefor. The innersurface 1827 comprises an equator line 1821, being the largest circularcircumference of the inner surface. The two extending portions passesbeyond the equator line 1821, such that and end portion 1829 of thecontacting portion, here being of the extending portion 1823 b of theinner surface 1827, forms a circular extension line 1822 placed distalto the equator line 1821, when the medical device is implanted, andhaving a smaller circumference than the equator line 1821; thus adistance 1826 between a center axis P of the medical device and theextension line 1822 is shorter than a distance 1825 between the centeraxis P and the equator line 1821.

FIG. 5 shows the medical device described with reference to FIG. 4 whenimplanted. According to this embodiment the medical device is adapted tobe fixated using orthopedic screws 1830, mechanically fixating themedical device to the pelvic bone 9, by the medical device comprisingholes through which the screws 1830 are placed. In FIG. 5 the contactingportion of the inner surface 1827 has been placed in contact with thespherical portion of a prosthetic caput femur 5 being fixated to aprosthetic collum femur 6, the prosthetic caput 5 and collum 6 femurreplacing the proximal portion of the femoral bone. The two extendingportions 1823 a and 1823 b extending the contacting portion of the innersurface and clasps the spherical portion of the prosthetic caput femur5, for restraining the spherical portion in the medical device. Theinner surface comprising the equator line 1821, and the extendingportions 1823 a,b passing beyond the equator line 1821 and comprisingthe more distal extension line 1822 having a smaller circumference thanthe equator line 1821. The more distal extension line 1822 being placedat a distance D1 from the equator line 1821. According to thisembodiment the extension the 1822 is parallel to the equator line 1821,however this is not necessarily so in other embodiments.

The extension portion 1823 a according to the embodiment shown in FIG. 5extends longitudinally along the equator line, a distance D2. Alonganother portion of the equator line, a distance D3, there are noextending portion, which enables the collum femur 6 to enter the spacebetween the first and second extending portions 1823 a,b which creates alarger movement range of the hip joint.

The extending portions thus extending discontinuously along the equatorline 1821, such that a portion of the collum femur 6 can be placedbetween the extension line 1822 and the equator line 1821.

The extending portion, according to any of the embodiments, adapted toclasp the caput femur or prosthetic replacement therefor for restrainingthe caput femur or prosthetic replacement therefor in the medicaldevice, could further be adapted to release the caput femur orprosthetic replacement therefor when a large enough strain is placed onthe joint. This feature enables the caput femur or prostheticreplacement therefor to be fixedly attached in the medical device innormal use and be released from the medical device e.g. in case of anaccident, thus reducing the risk of damaging the bodily structures, suchas the femoral bone, or the fixations between bodily structures andprosthetic parts, such as the fixation between the femoral bone and aprosthetic stem to which the prosthetic collum and caput femur isfixated.

According to one embodiment the extending elements, as for exampledisclosed with reference to FIGS. 1-5, are placed such that theextending elements restricts the motion range minimally, or in wayswhich are not limiting the motion range used in everyday life. The hipjoint is a synovial ball and socket joint which permits a large motionrange for allowing a plurality of different movements of the lower limb.From a neutral position the following movements of the hip joint arenormally possible: Lateral or external rotation, 30° with the hipextended, 50° with the hip flexed, medial or internal rotation 40°,extension or retroversion 20°, flexion or anteversion 140°, abduction60° with hip extended, 80° with hip flexed, adduction 30° with hipextended, 20° with hip flexed. In the movement ranges of abduction andadduction the depth of the acetabulum bowl and thus the extendingportions does not restrict the motion range in a critical way since themotion range of the normal hip is restricted in these movements, innormally agile persons, by the muscles, tenors and ligaments surroundingthe hip joint.

FIG. 6a shows a frontal view of pubis and the proximal portions of thefemoral bones 7 when two embodiments of the medical device has beenimplanted in the hip joint. The medical device shown placed on the rightcaput femur 5 a and placed in the right acetabulum 8 a comprises oneextending portion 1823, here placed dorsal to the proximal-distal axisY, thus only partially limiting abduction in far excess of 50°.According to the embodiment shown, the extending portion 1823 extendslongitudinally along the equator line 1821 about 1/10 of the length ofthe equator line 1821, however in other embodiments the extendingportion 1823 extends along as much as half of the length of the equatorline 1821, and in other embodiments the extending portion 1823 extendsas little as about 1/30 of the length of the equator line 1821. Themedical device shown placed on the left caput femur 5 b and placed inthe left acetabulum 8 b comprises two extending portions 1823 a,b, bothbeing placed dorsal to the proximal-distal axis Y, when implanted, thuslimiting the motion range of the hip joint in a non restrictive way, inrelation to everyday activities. In both the right and left embodimentthe extending portions 1823 extends discontinuously along the equatorline 1821 thus enabling the collum femur 6 to partially be placedbetween the equator line and the extension line, and in the leftembodiment placed between the extending portions 1823 a,b thus enteringthe cavity between the extending portions 1823 a,b.

FIG. 6b shows a frontal view of pubis and the proximal portions of thefemoral bones 7 when two further embodiments of the medical device havebeen implanted in the hip joint. The medical device shown placed on theright caput femur 5 a and placed in the right acetabulum 8 a comprisesone extending portion 1823, here placed in the proximal quadrant, whichis further disclosed with reference to FIG. 3, thus limiting the motionrange of the hip joint in a non restrictive way, in relation to everydayactivities. According to the embodiment shown, the extending portion1823 extends longitudinally along the equator line 1821 about 1/10 ofthe length of the equator line 1821, however in other embodiments theextending portion 1823 extends along as much as half of the length ofthe equator line 1821, and in other embodiments the extending portion1823 extends as little as about 1/30 of the length of the equator line1821. The medical device shown placed on the left, caput femur 5 b andplaced in the left acetabulum 8 b comprises two extending portions 1823a,b, being placed in the proximal and distal quadrants, thus limitingthe motion range of the hip joint in a non restrictive way, in relationto everyday activities.

FIG. 7 shows the pelvis and the proximal portions of the femoral bones 7including the embodiment of FIG. 6a , with the difference that thenatural caput femur and a portion of the natural collum femur has beenreplaced by a prosthetic caput femur 1833 and a prosthetic collum femur1832. The prosthesis further comprises a prosthetic stem 1831 adapted tobe placed inside and fixated to the femoral bone, either using bonecement or by the surface of the stem being adapted to facilitate thegrowth-in of bone, thus fixating the stem. The prosthetic collum femur1832 could be coordinated with the extending portions 1823 of themedical device for further improving the motion range of the hip joint,or not limiting the natural motion range of the hip joint.

FIG. 8 shows the medical device according to an embodiment in which themedical device comprises two extending portions 1823 a,b. The medicaldevice is placed on a prosthetic collum femur 1832, to which aprosthetic caput-femur 1833 is attached. The prosthesis furthercomprises a stem 1831 which is adapted to be fixated inside of thefemoral bone 7. The prosthetic collum femur 1832 is here adapted tofurther improve the motion range of the hip joint or not limiting thenatural motion range of the hip joint by the prosthetic collum femur1832 comprising a cavity 1834 in which the extending portions 1823 canbe placed.

FIG. 9a shows the pelvis in a lateral view, the medical device comprisestwo extending portions 1823 a,b, both extending longitudinally along theequator line (as disclosed in for example FIG. 5) dorsal to theproximal-distal axis Y and being adapted to clasp the caput femur or aprosthetic replacement therefor. The extending portions 1823 a,bextending dorsal to the proximal-distal axis Y and thus reducing thelimiting effect that the extending portions 1823 a,b, have on the motionrange of the hip joint. According to the embodiment shown in FIG. 9a theextending portion 1823 a placed proximally in the acetabulum extendslongitudinally a distance of about ¼ of the length of the equator line,and the extending portion 1823 b placed distally in the acetabulumextends longitudinally a distance of about 1/10 of the length of theequator line, however it is equally conceivable that this relationshipis the other way around, or that any of the extending portionslongitudinally extends a distance of as much as half of the length ofthe equator line, thus extending the entire distance of the equator linebeing dorsal to the proximal-distal axis, or that any of the extendingportions 1823 a,b extends a distance feeing as little as 1/30 of thedistance of the equator line. According to the embodiment shown in FIG.9a , the first extending portion 1823 a extends in distal-lateraldirection from the acetabulum, and the second extending portion 1823 bextends medially towards foramen obturatum.

FIG. 9b shows the pelvis in a lateral view, the medical device comprisestwo extending portions 1823 a,b, the two extending portions 1823 a,bextends in the proximal quadrant 1811 and the distal quadrant 1813,respectively.

There are multiple ways in which the extending portions 1823 can beadapted to reduce the effects that the extensions have on the motionrange of the hip joint.

FIG. 10 shows the pelvis in a lateral view, the medical device showncomprises one extending portion 1823 extending and being adapted toclasp the caput femur, or a prosthetic replacement therefor. Theextending portion 1823 extends longitudinally along the equator linewithin the proximal quadrant 1811, which is further disclosed withreference to FIG. 3. According to the embodiment, shown in FIG. 10, theextending portion 1823 extends in distal-lateral direction from theacetabulum.

FIG. 11 shows the pelvis in a lateral view, the medical device showncomprises a continuously extending portion 1823 with two extendingportions 1823 a and 1823 b extending further in relation to the averageextension of the extending portion. The entire extending portion isplaced in the proximal, distal and dorsal quadrants and the extendingportions 1823 a,b extending further than the average extension of theextending portion 1823 extends in the proximal and distal quadrant.

FIG. 12 shows the pelvis in a lateral view, the medical device showncomprises four extending portions 1823 a,b,c,d, wherein the first 1823 aand second 1823 b extending portions extends in the proximal and distalquadrant respectively, thus the first extending portion 1823 a extendingin distal-lateral direction from the acetabulum, and the secondextending portion 1823 b extending medially towards foramen obturatum.The third extending portion 1823 c extending in the frontal quadrant1812, out from the acetabulum in dorsal direction, extends less than thefirst and second extending portion, since extending portions 1823 c inthe frontal quadrant is more limiting to the normal motion range of thehip joint. The fourth extending portion 1823 d extends in the dorsalquadrant in accordance with the third extending portion 1823 c do notextend as far as the first and second extending portions.

FIG. 13 shows an alternative embodiment of the medical device. In thealternative embodiment the medical device comprises a first part 1841adapted to be fixated to the pelvic bone of the patient. The first partcomprises an inner contacting surface adapted to be in movableconnection with an outer contacting surface of a second part 1842. Thesecond part 1842 is rotatably fixated to the first part 1841 by arotatable connecting member 1843. An outer contacting surface of aprosthetic caput femur 1833 is adapted to be placed in contact with theinner surface of the second part 1842 and be movable in multipledirections, thus replicating the natural ball and socket joint of thehip. The second part 1842 comprises two extending portions 1823 a, bextending beyond the equator line 1845 of the second part 1842. Theextending portions 1823 a,b extends longitudinally discontinuously alongthe equator line, thus creating an area between the extending portions,in which area a portion of the prosthetic collum femur can be placed,thus being placed partially between the equator line 1845 and theextension line 1846. The construction shown in FIG. 13 enables thesecond part 1842 to rotate if the collum femur 1832 engages theextending portions 1823 a,b, which are sloped for this purpose. This waythe second part 1842 are always placed such that the collum femur 1832can be placed partially between equator line 1845 and the extension line1846, which creates an optimal range of movement whilst the second partclasps the prosthetic caput femur 1833, and thus restricting the caputfemur 1833 in the second part 1842 of the medical device. According tothe embodiment shown the caput and collum femur is a prosthetic caput1833 and collum 1832 femur, comprising a prosthetic stem 1831 adapted tobe fixated in the femoral bone 7, however, in other embodiments, it isequally conceivable that the natural caput femur is resurfaced andplaced in the second part 1842.

FIG. 14a shows the medical device 65 in a perspective view from belowaccording to one embodiment in this embodiment the medical devicecomprises two extending portions 1823 a, b. The medical device 65 isaccording to this embodiment adapted to be fixated to the pelvic bone bymeans of an adhesive which is adapted to be placed in connection withthe adhesive recesses 1870 of the outer surface of the medical device65.

FIG. 14b shows a medical device similar to the medical device disclosedwith reference to FIG. 14a , but with the difference that it comprisesthree equally extending portions 1823 a,b,c.

FIG. 14c shows a medical device similar to the medical device disclosedwith reference to FIG. 14a , but with the difference that it comprisestwo equally extending portions 1823 a,b and one less extending portion1823 c.

FIG. 14b shows a medical device similar to the medical device disclosedwith reference to FIG. 14a , but with the difference that it comprisesfour equally extending portions 1823 a,b,c,d.

FIG. 14b shows a medical device similar to the medical device disclosedwith reference to FIG. 14a , but with the difference that the twoextending portions are placed further from each other, and thus beingadapted to be placed in the proximal and distal quadrant, whenimplanted.

FIG. 14b shows a medical device similar to the medical device disclosedwith reference to FIG. 14a , but further comprising a less extendingportion 1823 c placed between the first and second extending portions1823 a,b.

The extending portions of the medical device which have been describedcould be made from an elastic material, enabling the extending portionsto pass onto the caput femur.

FIG. 15a shows the medical device in an embodiment in which the medicaldevice is fixated to the pelvic bone 9. The medical device comprisesextending portions which in turn serves as releasing members 801adapted, in a first state, to hold the caput femur in the medical deviceand in a second state release the caput femur 5 from the medical device.The releasing member 801 is adapted to change from the first state tothe second state when a predetermined strain is placed on the releasingmember 801. The strain could be caused by an abnormal movement of thehip joint e.g. as the result of the patient falling. According to theembodiment shown in FIG. 14 the releasing member 801 comprises anelastic portion comprising elastic material, in the embodiment shownbeing the entire releasing member 801. The releasing member is adaptedto non-invasively be able to change from the first state to the secondstate and from the second state to the first state, when apre-determined strain is placed on the releasing member 801 i.e.

FIG. 15b shows the hip joint in section when the releasing member 801 isin its second state, wherein the releasing member 801 is adapted torelease the caput femur 5 from the medical device placed in the pelvicbone 9. The releasing member 801 has changed from the first state to thesecond state because a pre-determined strain has been placed on thereleasing member 801.

FIG. 16 shows the medical device according to an embodiment where themedical device comprises holding members 802 a,b, adapted to slideagainst, the caput femur 5, or a prosthetic replacement therefore. Theholding members are adapted to, in a first state, hold the caput femur5, or a prosthetic replacement therefore, in a second state thereleasing member 801 is adapted to release the caput femur 5, or aprosthetic replacement therefore, from the medical device placed in thepelvic bone 9. The holding members 802 a,b are spring loaded through aspring 803 a,b being placed between a calibration member, being acalibration screw 804 a,b, and die holding members 802 a,b. The forceexerted on the holding members 802 a,b from the spring 803 a,b isadapted to hold the caput lemur 5, or a prosthetic replacementtherefore, in the medical device in normal, functional hip jointmovements, but release the caput femur 5, or a prosthetic replacementtherefore, from the medical device when, a pre-determined strain isplaced on the releasing member which could be caused by an abnormalmovement of the hip joint, e.g. as the result of the patient falling.The calibration screws 804 a,b enables the pre-determination of thestrain which will cause the holding members 802 a,b to change from beingin a first state to being in a second state.

FIG. 17 shows the releasing members in their second state, when apre-determined strain has been exceeded, preferably being caused by anabnormal movement of the hip joint, e.g. as the result of the patientfalling. The holding members 802 a,b are retracted into sleeves 806 ofthe medical device, thereby compressing the springs 803 a,b. Theretraction of the holding members 802 a,b causes the caput femur 5, or aprosthetic replacement therefore, to be dislocated/luxated from itsposition in the medical device, which, when large strain is placed onthe hip joint and femoral bone 7, reduces the risk of the patientfracturing the femoral bone 7 or the pelvic bone 9. The holding members802 a,b are adapted to non-invasively be able to change from the firststate to the second state and from the second state to the first state,when a predetermined strain is placed on the holding members 802 a,b.

FIG. 18 shows the medical device in section, with the holding members802, placed in sleeves 806 evenly distributed along the cross-section ofthe medical device, holding the caput femur 5, or a prostheticreplacement therefore, in position in the medical device.

FIG. 19 shows an alternative embodiment of the principle shown in FIGS.16-18, wherein the holding members 802 a,b, comprises ball shapedmembers 805 a,b in contact with the caput femur 5, or a prostheticreplacement therefore, and being adapted to roll against the caput femur5, or a prosthetic replacement therefore, holding the caput femur 5, ora prosthetic replacement therefore, in place in the medical device, bythe holding members 802 a,b exerting force on the caput femur 5, or aprosthetic replacement therefore, through the contact with the springs803 a,b supported by the calibration screws 804 a,b.

FIG. 20 shows the releasing members in their second state, when apre-determined strain has been exceeded, preferably being caused by anabnormal movement of the hip joint e.g. as the result of the patientfalling. The holding members 802 a,b, comprising the ball shaped members805 a,b, are retracted into sleeves 806 of the Medical device, therebycompressing the springs 803 a,b. The retraction of the holding members802 a,b causes the caput femur 5, or a prosthetic replacement therefore,to be dislocated/luxated from its position in the medical device, which,when large strain is placed on the hip joint and femoral bone 7, reducesthe risk of the patient fracturing the femoral bone 7 or the pelvic bone9. The holding members 802 a,b are adapted to non-invasively be able tochange from the first state to the second state and from the secondstate to the first state, when a pre-determined strain is placed on theholding members 802 a,b, which enables the caput femur 5, or aprosthetic replacement therefore, to be replaced in the medical devicewithout a surgical procedure.

FIG. 21 shows the medical device in an embodiment wherein the releasingmembers 801 comprises a rupture device 807, 808, 809 adapted to tail ata pre-determined strain. According to this embodiment the rupture deviceis a rupture pin 807, 808, 809 comprising a base part 809 a,b fixated totire medical device and a rupture part 807 a,b attached to tire basepart 809 a,b through a weakened section 808 a,b, in which section tirerupture part 807 a,b is detached from the base part 809 a,b when apredetermined strain is placed on the rupture device in contact with thecaput femur 5, or a prosthetic replacement therefore.

FIG. 22 shows the medical device according to the embodiment of FIG. 21when the rupture device has failed due to a predetermined strain on therupture device being exceeded. According to one embodiment (not shown)the rupture parts 807 a,b are secured to the base part-through asecurity wire keeping rupture parts 807 a,b in proximity to the basepart 809 a,b even after the failure of the rapture device.

FIG. 23a shows the medical device according to an embodiment where themedical device comprises a circular sleeve 806, in which an elastic orrupture band 810 is provided. The elastic or rupture band 810 is adaptedto at least partly encircle the ball shaped caput femur 5, or prostheticreplacement therefore. When a pre-determined strain is placed on theelastic or rupture band 810 the circular opening encircling the caputfemur 5, or a prosthetic replacement therefore, is expanded and thecaput femur 5, or a prosthetic replacement therefore, is released fromthe medical device, to which it is held by means of the elastic band610. In embodiments where the medical device comprises a rupture band810 holding the caput femur 5, or a prosthetic replacement therefore, inthe medical device, a weakened portion 811 of the band 810 fails andthus the circular opening encircling the caput femur 5, or a prostheticreplacement therefore, is expanded and the caput femur 5, or aprosthetic replacement therefore, is released from the medical device.In the embodiments where the band 810 is an elastic band 810 it isconceivable that the band 810 camp rises an elastic part or section, orthat the entire band 810 is made of an elastic material.

FIG. 23b shows the medical device in section when the elastic orrapturing band 810, holding the caput femur 5, or a prostheticreplacement therefore, is placed in a circular sleeve 806 in the medicaldevice. An opening or weakened portion 811 is provided perpendicular tothe circumference of the band 810.

FIG. 24a shows the medical device in a second state where the caputfemur 5, or a prosthetic replacement therefore, is released from theconnection with the medical device, after a pre-determined stain hasbeen placed on the elastic or rupture band 810. As shown in FIG. 24b ,the gap or weakened part has been expanded, thereby allowing the caputfemur, or a prosthetic replacement therefore, 5 to pass through theopening defined by the elastic or rupture band 810. The medical devicecould be adapted to non-invasively be able to change from the firststate to the second state and from the second state to the first state,when a pre-determined strain is placed on the band 810, which enablesthe caput femur 5, or a prosthetic replacement therefore, to be replacedin the medical device without a surgical procedure.

FIG. 25 shows the medical device according to an embodiment where thereleasing member 801 comprises an elastic wing of the medical device,which is assisted by an elastic or rupture band 810 encircling themedical device by enclosing the caput femur 5, or a prostheticreplacement therefore, in the medical device passing beyond the point ofthe caput femur 5, or a prosthetic replacement therefore, having alargest cross-sectional distance. The elastic or rupture band 810 isheld in place to the medical device by means of the band 810 beingplaced in a groove along the circumference of the medical device.However, said groove could be assisted or replaced by an adhesive or amechanical fixation element.

FIG. 26 shows the medical device when in its second state, in which thereleasing member 801 releases the caput femur 5 or a prostheticreplacement therefore, from the medical device. In embodiments when theband 810 is an elastic band 810 it could be expanded, thereby enlargingthe tele through which the caput femur 5, or a prosthetic replacementtherefore, can pass. In embodiments where the band 810 is a ruptureband, the band 810 fails and thereby the caput femur 5, or a prostheticreplacement therefore, is held in place solely by the releasing member801 which is a part of the extending portion adapted to release thecaput femur 5, or a prosthetic replacement therefore, at a pre-definedstrain. The medical device could be adapted to noninvasively be able tochange from the first state to the second state and from the secondstate to the first state, when a pre-determined strain is placed on theband 810 and/or the releasing member 801, which enables the caput femur5, or a prosthetic replacement therefore, to be replaced in the medicaldevice without a surgical procedure.

FIG. 27 shows the hip joint in section according to an embodiment wherethe caput femur 5, or a prosthetic replacement therefore, and collumfemur 6 have been replaced with a prosthetic part 818 fixated to thefemoral bone 7, either with bone cement, or without. The prosthetic part818 comprises a prosthetic caput femur 812 having a cavity 816 in whicha rupture band 813 fixated to a fixation portion 814 of the prostheticcaput femur 812, and a fixating portion 815 of the medical device. Thecavity 816 is adapted to enable the prosthetic caput femur 812 toperform normal functional hip movements inside the medical device. Therupture band 813 is adapted to hold the prosthetic caput femur 812 tothe medical device in a first state, and release the prosthetic caputfemur 812 from the medical device when, a pre-determined strain isplaced on the rupture band 813.

FIG. 28 shows the embodiment of the medical device according to FIG. 27,in a second state in which the rupture band 813 has failed and therebythe prosthetic caput femur 812 is released from the medical device. Therupture band 813 could be fixated to a fixation portion 814 of theprosthetic caput femur 812, and/or a fixating portion 815 of the medicaldevice using: at least one screw, at least one pin, form fitting,welding, adhesive, pin, wire, a ball mounted into a bowl, a male portionof one part mounted into a female portion of the other part a keyintroduced into a lock being portions of said parts, band, or othermechanical connecting members. The failing of the rupture band 813 iswhich could be caused by an abnormal movement of the hip joint, e.g. asthe result of the patient falling.

FIG. 29 shows a prosthetic part 818 according to an embodiment where theprosthetic part 818 is fixated to the femoral bone 7 and comprises acaput femur 812 comprising a cavity 816 adapted to enable the hip jointto perform functional hip joint movements while in a first state held tothe medical device using an elastic bend 817 fixated to a fixationportion 814 of the prosthetic caput femur 812, and a fixating portion815 of the medical device, and a releasing member 801 according to theembodiment shown in FIGS. 9 and 10. The combination of the releasingmember 801 and the elastic band 817 is adapted to, in a first state holdthe prosthetic part 818 to the medical device, and in a second staterelease the prosthetic part 818 from the medical device. According toanother embodiment (not shown) the prosthetic part is held to themedical device solely using the elastic band 817, of course alsosupported by the remainder of hip joint capsule and the affectedmuscles. FIG. 29 shows a prosthetic caput femur 812 and a prostheticacetabulum comprising the releasing member 801. A totally prostheticembodiment is conceivable with regards to all of the embodiments of thereleasing members disclosed herein. In any of these embodiments i.e. inembodiments where both the caput femur and the acetabulum are prostheticparts, the prosthetic caput femur and prosthetic acetabulum could bepre-mounted when implanted in a patient such that one unit is implantedin the patient comprising the functioning hip joint.

FIG. 30 shows the embodiment of the medical device according to FIG. 29,in a second state in which the elastic band 817 is stretched such thatthe prosthetic part 818 is released from the medical device. The elasticband 817 could be fixated to a fixation portion 814 of the prostheticcaput femur 812, and/or a fixating portion 815 of the medical deviceusing: at least one screw, at least one pin, form fitting, welding,adhesive, pin, wire, a ball mounted into a bowl, a male portion of onepart mounted into a female portion of the other part, a key introducedinto a lock being portions of said parts, band, or other mechanicalconnecting members. The failing of the rupture band 813 is preferablycaused by an abnormal movement of the hip joint, e.g. as the result ofthe patient falling. The elastic band 817 could comprise an elastic partor section, which could be the entire elastic band 818, made from anelastic material, such as an elastic polymer material such as: acopolymer material such as polystyrene, poly(ethylene-butylene) orpolystyrene. It is also conceivable that the material is a polyurethaneelastomeric material, polyamide elastomeric materials and polyesterelastomeric materials elastic copolymers of ethylene and at least onevinyl monomer such as, for example, vinyl acetates, unsaturatedaliphatic monocarboxylic acids, and esters of such monocarboxylic acids.The elastic band 813 could comprise a barrier coating, which cannot bepenetrated by body cells. Preferably, the barrier coating comprises aParylene™ coating, or a biocompatible metal coating, such as gold,silver or titanium. According to other embodiments the elastic bandcomprises a spring type member, a combination of metal and plasticmaterials, a combination of metal and carbon based material or acombination of carbon and plastic based material.

FIG. 31 shows the hip joint section in an embodiment where the medicaldevice comprises a prosthetic part 819 adapted to be fixated to thefemoral bone 7. The prosthetic part comprises a prosthetic caput femurwhich is adapted to comprise elastic elements 820 which act as areleasing member holding the prosthetic caput femur inside of themedical device fixated to the pelvic bone. The elastic elements 820 ofthe prosthetic caput femur, is preferably made of an elastic material,which for example could be an elastomeric polymer material or an elasticmetal material. His conceivable that the elastic material comprises anouter layer in connection with the medical device which is adapted toresist the wear from the contact with the medical device. The elasticelement is adapted to comprises when a predetermined strain is placed onthe hip joint and thereby on foe elastic elements 820. When the elasticelements 820 are compressed foe prosthetic caput femur is released fromthe medical device.

FIG. 32 shows the medical device according to the embodiment shown inFIG. 31, in a second state, in which the elastic element 820 has beencompressed, following a pre-determined strain being placed on themedical device. The medical device is thereby placed in a second state,in which the prosthetic caput femur is released from the medical device,wherein it has been held.

FIG. 33 shows an embodiment of the medical device in which the elasticelements 820 are further assisted by a spring 821 in connection with twoelastic elements 820, the spring 821 is compressed alongside foe elasticmembers 820, when a pro-determined strain is placed on the prostheticpart 819 comprising the prosthetic caput femur.

FIG. 34 shows the hip joint in section when a medical device for, in afirst state, holding the caput femur 5, or a prosthetic replacementtherefore, to the medical device, and in a second state releasing thecaput femur 5, or a prosthetic replacement therefore from the medicaldevice. The medical device is adapted to change from being in the firststate to being in the second state at a pre-determined strain affectingthe medical device by the connection with the pelvic bore 9 and thefemoral bone 7, which reduced the risk of the patient fracturing thefemoral bone 7 and/or the pelvic bone 9. The medical device comprisesmagnets 823 or magnetic material 823 placed in the medical device, andmagnets 822 or magnetic material 822 placed in the caput femur 5 or aprosthetic replacement therefore. According to one embodiment a magnet823 is placed in the medical device its south pole directed towards thecaput femur 5, or prosthetic replacement therefore, and a magnet 822placed in the caput femur 5, or prosthetic replacement therefore, havingits north pole directed towards the medical device. However only one ofthe sides needs to be magnetic whereas the other side merely needs tocomprise magnetic material. Any combination of north and south ends andmagnets/magnetic material is hence conceivable. The magnetic forcedescribed is adapted to hold the caput femur 5, or a prostheticreplacement therefore, in the medical device in normal use, enabling thehip joint to perform functional hip joint movements, and release thecaput femur 5, or a prosthetic replacement therefore, from the medicaldevice when a predetermined strain is exceeded.

FIG. 35 shows the medical device according to the embodiment of FIG. 30in the second state, in which the caput femur 5, or a prostheticreplacement therefore, is released from the medical device as a resultof a predetermined level of strain being exceeded.

The medical device according to any of the embodiments could comprise atleast one material selected from a group consisting of:polytetrafluoroethylene (PIFE), perfluoroalkoxy (PFA) and fluorinatedethylene propylene (FEP). It is furthermore conceivable that thematerial comprises a metal alloy, such as cobalt-chromium-molybdenum ortitanium or stainless steel, or polyethylene, such as cross-linkedpolyethylene or gas sterilized polyethylene. The use of ceramic materialis also conceivable, in the contacting surfaces or the entire medicaldevice such as zirconium or zirconium dioxide ceramics or aluminaceramics. The part of the medical device in contact with human bone forfixation of the medical device to human bone could comprise a poorhousestructure which could be a porous micro or nano-structure adapted topromote the growth-in of human bone in the medical device for fixatingthe medical device. The porous structure could be achieved by applying ahydroxy-apatite (HA) coating, or a rough open-pored titanium coating,which could be produced by air plasma spraying, a combination comprisinga rough open-pored titanium coating and a HA top layer is alsoconceivable. The contacting parts could be made of a self lubricatedmaterial such as a waxy polymer, such as PIFE, PFA, FEP, PE and UHMWPE,or a powder metallurgy material which could be infused with a lubricantwhich preferably is a biocompatible lubricant such as a Hyaluronic acidderivate. It is also conceivable that the material of contacting partsor surfaces of the medical device herein is adapted to be constantly orintermittently lubricated. According to some embodiments the parts orportions of the medical device could comprise a combination of metalmaterials and/or carbon fibers and/or boron, a combination of metal andplastic materials, a combination of metal and carbon based material, acombination of carbon and plastic based material, a combination offlexible and stiff materials, a combination of elastic and less elasticmaterials, Corian or acrylic polymers.

Please note that any embodiment or part of embodiment as well as anymethod or part of method could be combined in any way. All examplesherein should be seen as part of the general description and thereforepossible to combine in any way in general terms.

The invention claimed is:
 1. A medical device for implantation in a hipjoint of a patient, wherein said medical device comprises an inner andan outer surface, wherein a contacting portion of said inner surface isspherical and adapted to face a center of the hip joint when saidmedical device is implanted, and wherein said medical device is adaptedto receive a caput femur or a prosthetic caput femur having a sphericalportion, wherein a) said medical device comprises at least one holdingmember for restraining said caput femur, or said prosthetic caput femurin said medical device, b) said at least one holding member is slidablein a direction more transversal to than parallel with a center axis of acollum femur, and wherein c) said medical device is adapted to releasethe caput femur or prosthetic caput femur from said medical device bysliding said at least one holding member away from the center axis ofthe collum femur when a predetermined strain is placed on said medicaldevice by abnormal movement of the hip joint caused by the patient. 2.The medical device according to claim 1, wherein said at least oneholding member is spring loaded towards the center axis of the collumfemur.
 3. The medical device according to claim 2, wherein said medicaldevice comprises a spring for each at least one holding member causingsaid spring load on each of the at least one holding member.
 4. Themedical device according to claim 1, wherein said at least one holdingmember is adapted to roll against the caput femur.
 5. The medical deviceaccording to claim 4, wherein said at least one holding member comprisesa ball shaped part adapted to roll against the caput femur.
 6. Themedical device according to claim 1, wherein said medical devicecomprises a second holding member for restraining said caput femur, orsaid prosthetic caput femur in said medical device.
 7. The medicaldevice according to claim 6, wherein said medical device comprises athird holding member for restraining said caput femur, or saidprosthetic caput femur in said medical device.
 8. The medical deviceaccording to claim 1, wherein said holding member comprises a metalmaterial.
 9. The medical device according to claim 1, wherein saidholding member comprises a ceramic material.
 10. The medical deviceaccording to claim 1, wherein said holding member comprises a polymermaterial.
 11. The medical device according to claim 10, wherein saidholding member comprises HDPE.
 12. The medical device according to claim1 further comprising at least one calibration member for calibrating thepre-determined strain which will release the caput femur or prostheticcaput femur from said medical device.
 13. The medical device accordingto claim 12, wherein said at least one calibration member is acalibration screw, being rotatable to set said predetermined strain. 14.The medical device according to claim 1, comprising a plurality ofholding members placed in sleeves evenly distributed around the caputfemur or a prosthetic replacement therefore.
 15. The medical deviceaccording to claim 1, wherein said at least one holding member is acircular elastic band.
 16. The medical device according to claim 15,wherein said medical device further comprises a circular sleeve in whichthe circular elastic band is slidably arranged.
 17. The medical deviceaccording to claim 16, wherein the circular elastic band comprises aweakened portion which may fail upon forces above said predeterminedforce.